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RUNNING HEAD: PROBLEM BEHAVIOR IN FRAGILE X AND SMITH-MAGENIS
SYNDROME
An Indirect Examination of the Function of Problem Behavior Associated with Fragile X
Syndrome and Smith-Magenis Syndrome
Paul Langthorne
Peter McGill
Tizard Centre, University of Kent Title Page with All Author Contact Information
Abstract
Fragile X syndrome (FXS) and Smith-Magenis syndrome (SMS) are associated with a number of specific topographies of problem behavior. Very few studies have examined the function served by problem behavior in these groups. Using the Questions About Behavioral Function scale (Matson & Vollmer, 1995) the current study examined group differences in the function of problem behavior displayed by children with FXS and SMS, in comparison to a control group of children with non-specific intellectual and developmental disabilities. Between- group analyses showed children with SMS were more likely to display problem behavior related to physical discomfort. Both within- and between-group analyses showed children with FXS were less likely to display attention-maintained problem behavior. These findings hold implications for the assessment, treatment and prevention of problem behavior associated with both FXS and SMS. Key words: functional assessment, problem behavior, fragile X syndrome, Smith-Magenis syndrome.
P.Langthorne@hotmail.com
Problem behavior in fragile X and Smith-Magenis syndrome 1 An Indirect Examination of the Function of Problem Behavior Associated with Fragile X
Syndrome and Smith-Magenis Syndrome
Approximately 10% of children with severe intellectual and developmental disabilities (IDD) display problem behavior, such as self-injurious behavior (SIB), aggression or property destruction (Kiernan & Kiernan, 1994). Children who display problem behavior are likely to be disadvantaged across a number of indices of quality of life (e.g., Borthwick-Duffy, 1994; Rusch, Hall, & Griffin, 1986). Such behaviors may also be a considerable source of stress for families and caregivers (Hastings, 2002). Genetic variables appear to be an important risk factor for the development of problem behavior in people with IDD (May et al., 2009). Indeed, problem behavior is considered to be phenotypic of a number of single gene disorder syndromes associated with IDD. Two syndromes where such gene-behavior associations have been widely investigated are fragile X syndrome (FXS) and Smith-Magenis syndrome (SMS). FXS is the most common inherited cause of IDD, occurring in 1:3,600 males and 1:8,000 females in the general population (Turner, Webb, Wake, & Robinson, 1996). The genetic locus of FXS lies in a mutation on a single gene on the X chromosome known as the FMR1 gene (Verkerk et al., 1991). This mutation, which consists of an amplification of CGG repeats, leads to hypermethylation of the promoter region of the FMR1 gene resulting in the reduced production of the Fragile X Mental Retardation Protein (FMRP), a protein that plays an important role in regulating brain development (Gothelf et al., 2008). Indeed, FXS appears to be associated with the heightened prevalence of both aggression (Einfeld, Hall, & Levy, 1991) and
SIB (Symons, Clark, Hatton, Skinner, & Bailey, 2003). SIB occurs in over 50% of boys with *BLIND Manuscript without contact information&OLFNKHUHWRGRZQORDG%/,1'0DQXVFULSWZLWKRXWFRQWDFWLQIRUPDWLRQ-$''BFDWHJRULFDOBRQO\BGRF&OLFNKHUHWRYLHZOLQNHG5HIHUHQFHV
Problem behavior in fragile X and Smith-Magenis syndrome 2 FXS and is particularly likely to involve hand-biting, although other topographies, such as head- hitting and skin picking also occur at elevated rates (Symons, Clark, Hatton, Skinner, & Bailey,
2003). Certain stereotypical behaviors, such as hand-flapping, also appear to occur at unusually
high rates in FXS (Meerenstein et al., 1996). SMS has an estimated prevalence of 1/25,000, with an equal distribution between the genders (Greenberg et al., 1991). SMS is caused by an interstitial deletion of chromosome
17p11.2, although recent research suggests that haploinsufficiency of the RAI1 gene is the
primary genetic cause of the syndrome (Edelman et al., 2007; Slager et al., 2003). Problem behaviors appear to form a relatively prominent feature of SMS (Clarke & Boer, 1998; Dykens & Smith, 1998). In comparison to other groups, SMS is associated with relatively high levels of aggression, as well as a range of stereotypical behaviors (Dykens, Finucane, & Gayley, 1997; Dykens & Smith, 1998). Estimates of the prevalence of SIB in SMS vary between 67-96% (Dykens & Smith, 1998; Finucane, Dirrigl, & Simon, 2001; Greenberg et al., 1996; Martin, Wolters, & Smith, 2006). Some topographies of SIB, such as onychotillomania (pulling out finger- and toenails) and polyembolokomania (insertion of objects into body orifices) appear to be relatively unique to the syndrome (e.g., Finucane, Dirrigl, & Simon, 2001). Research on FXS and SMS to date has predominantly examined the form of problem behavior rather than its function. Functional assessment methodologies aim to identify those variables that evoke and maintain problem behavior. Problem behavior displayed by people with IDD has been repeatedly demonstrated to serve an operant function with such behaviors being commonly maintained by socially- and non-socially mediated forms of positive and negative reinforcement (e.g., Hanley, Iwata, & McCord, 2003). These relations appear to influence problem behavior even in cases where those behaviors are recognised as being phenotypic of a Problem behavior in fragile X and Smith-Magenis syndrome 3 particular syndrome (e.g., Hall, Oliver, & Murphy, 2001; Sloneem, Arron, Hall, & Oliver, 2009; O'Reilly, Lacey, & Lancioni, 2000). It seems unlikely, therefore, that genes have an effect on problem behavior independent of environmental influence (Langthorne & McGill, 2008). It has been suggested that developmental changes associated with certain genetic syndromes may influence the occurrence of problem behavior by altering the reinforcing value of some of the consequences that commonly maintain such behaviors (Kennedy, Caruso, & Thompson, 2001; Langthorne & McGill, 2008; Oliver, 1993). If, in some cases, genetic events - and within-syndrome) in the function served by problem behavior across certain syndrome groups should be expected. There is some preliminary evidence to indicate that people with FXS and SMS may differ in the probability of displaying problem behaviors that serve certain functions. It appears that individuals with FXS may be less likely to display problem behavior that is maintained by the provision of social attention than would typically be expected and more likely to be maintained by the removal of aversive stimuli, and/or the provision of tangibles (Hall, DeBernadis, & Reiss,
2006; Roberts, Weisenfeld, Hatton, Heath, & Kaufmann, 2007; Symons, Clark, Hatton, Skinner,
& Bailey, 2003; Woodcock, Oliver, & Humphreys, 2009). Symons et al for example, using a modified Sprague, 1990) reported that only 3% of children with FXS displayed attention-maintained SIB. In comparison, 65-87% were reported to display SIB in response to task demands and changes in routine. Others have noted the apparent high levels of social escape and avoidance behaviors associated with FXS (Hall et al., 2006; Roberts et al., 2007). Problem behavior in fragile X and Smith-Magenis syndrome 4 In contrast several clinical reports and studies of SMS (e.g., Bass & Speak, 2005; Dykens & Smith, 1998; Smith, Dykens, & Greenberg, 1998) have noted the apparently high level of behaviors associated with the syndrome. A recent study by Taylor and Oliver (2008) involving descriptive functional assessment methods reported that for four out of the five children with SMS in their study, problem behavior was more likely to occur following periods of low adult attention or following reduced levels of demands and was likely to lead to an increase in attention or demands for those same children. Such evidence indicates that attention may hold different reinforcing properties for children with SMS than for other groups, such as children with FXS. The current study aimed to further this line of research by examining problem behavior displayed by children with FXS and SMS, in comparison to one another and to a control group of children with non-specific IDD. This is the first study of which we are aware to have examined between-syndrome differences in the function of problem behavior. The Questions About Behavioral Function scale (QABF; Matson & Vollmer, 1995) was used to provide a more robust indirect measure of behavioral function.
Method
Participants
Participants were individuals with IDD aged 5-21 years who were reported to display at least one of the following topographical classes of problem behavior: self-injury, aggression or property destruction. Participants belonged to one of three etiological groups: FXS, SMS, or non- specific IDD. There were 34 participants with FXS, 25 with SMS and 30 with a non-specific IDD. Problem behavior in fragile X and Smith-Magenis syndrome 5 All participants from the FXS and non-specific IDD groups were recruited via relevant parental support groups based in the United Kingdom. Participants from the SMS group were recruited via a combination of the following methods; via parental support groups (N= 5), via regional genetics testing centres (N= 7) and via word of mouth and advertisement in relevant publications (N= 13). All participants with FXS and SMS had a confirmed genetic diagnosis and evidence of this was requested by the researchers. In cases where this was not forthcoming, parents were genetic testing centre or paediatrician.
Procedure and Measures
The study received multi-site ethical approval from the National Health Service and from the Tizard Centre Ethics Committee. All participants were sent information about the study and were asked to return a completed consent form indicating a convenient time for the interviews to be conducted and a completed copy of the Aberrant Behavior Checklist- Community Version (Aman, Burrow, & Wolford, 1995). All remaining measures were conducted with parents/caregivers over the telephone. Parents were sent paper copies of all questionnaires in advance and were prompted to have all measures to hand when completing the telephone interview. All interviews began with the researcher establishing whether this was a convenient time for the interview. If necessary, interviews were rearranged for an alternative time. The Vineland Adaptive Behavior Scale-Screener version (Sparrow, 2000) and the QABF (Matson & Vollmer,
1995) were completed as part of the interview.
Problem behavior in fragile X and Smith-Magenis syndrome 6 The QABF was completed for each general category of problem behavior (aggression, self-injury, and property destruction) the child was reported to display. The QABF provides
4-point scale. Total scores for each subscale
were then calculated. the scale has good reliability (Paclawskyj, Matson, Rush, Smalls, & Vollmer, 2000) and predictive and convergent validity (Matson, Bamburg, Cherry, & Paclawskyj, 1999; Paclawskyj, Matson, Rush, Smalls, & Vollmer, 2001). The QABF has been used to measure behavioral function in a number of other large N studies (e.g., Didden, Korzilius, & Curfs, 2007). To prevent individual variation in QABF scale scores being masked by the aggregation of individual scores, the data used in the current study were analyzed categorically. Various approaches to the categorical analysis of the QABF have been used (see Matson & Vollmer, 1995; Matson & Boisjoli, 2007; Paclawskyj, Matson, Rush, Smalls, & Vollmer,
2001). As many participants were reported to display behaviors that were potentially multi-
functional, a relatively high cut-off score of 10 was selected as it is the lowest total scale score requiring that a minimum of 4 items be endorsed.
Statistics
Participant age and severity of problem behavior were analyzed using one-way ANOVAs at a significance level of 0.05. Differences in the gender of the groups was examined using a chi square test at a significance level of 0.05. As the data for the Vineland Adaptive Behavior Scales were not normally distributed a series of non-parametric Kruskal-Wallis tests were used to examine group differences across all sub-domains. To reduce the Problem behavior in fragile X and Smith-Magenis syndrome 7
Į0.05 was divided by
the number of comparisons made, resulting in a significance level of 0.012. Henceforth where the same process has been used to account for multiple comparisons, this shall be referred to as the Bonferroni adjustment. Mann Whitney tests were used to examine post hoc between-group differences on the Vineland using a significance level of 0.016 (Bonferroni adjustment). Between-group differences in the proportion of participants who displayed problem behavior that served single compared to multiple functions were analyzed using a series of chi-square tests at a significance level of 0.012 (Bonferroni adjustment). Within-group differences in the proportion of participants with FXS who met criteria for attention-maintained problem behavior in comparison to other functions were examined using a series of Cochran Q tests at a significance level of 0.016 (Bonerroni adjustment). Within-group pairwise differences were then examined using a series of McNemar tests at a significance level of 0.012 (Bonferroni adjustment). Between group differences in the proportion of participants who met criteria for specific functions on the QABF were analyzed using a series of chi-square tests at a significance level of 0.003 (Bonferroni adjustment).
Results
Table 1 shows participant characteristics for each group. Participants in all three groups were matched for age (F [2, 85] = 1.195; p> 0.05), severity of overall problem behavior (F [2,
85] = 1.065; p>0.05) as measured by the Aberrant Behavior Checklist (Aman, Singh, Stewart, &
Field, 1985). There were significantly more females in the SMS group than the other two groups Problem behavior in fragile X and Smith-Magenis syndrome 8 DQGWKH6RFLDOL]DWLRQVXEGRPDLQ$ S!7KHUHZHUHVLJQLILFDQWEHWZHHQJURXS Pairwise comparisons showed scores for the SMS group were significantly greater than both the FXS group (U = 203; p< 0.016), and the mixed etiology group (U= 157.5; p<0.016). Differences between children with FXS and the mixed etiology group were not significant (U= 403; p >0.016). A total of 2.9% of participants in the FXS group, 4.0% of those in the SMS group and
20.0% in the non-specific IDD group were reported to present with one topographical class of
problem behavior, 51.4%%, 17.1% and 36.7% in each respective group presented with two topographical classes of problem behavior and 45.7%, 72.0% and 43.3% in each group presented with three topographical classes of problem behavior. [Insert Table 1 about here] Table 2 shows the percentage of participants in each group who presented with behaviors that served a single versus multiple function across each topographical class of problem behavior, as well as those participants in each group for whom no function was identified. There were no significant between-group differences in the proportion meeting criteria for behavioral function for self-injury or aggression, there were, however, significant differences for property [Insert Table 2 about here] Figure 1 shows the percentage of participants in each group who met criteria for each subscale of the QABF across each topographical class of problem behavior. Problem behavior in fragile X and Smith-Magenis syndrome 9 [Insert Figure 1 about here] Examination of the within-group data for participants with FXS suggests the proportion of participants meeting criteria for the attention subscale of the QABF was lower than for other scales. For self-injury, 6.7% of the group were identified as displaying attention-maintained behavior, 43.3% as tangible-maintained, 40.0% as escape-maintained, 30.0% as discomfort- related and 23.3% as self-stimulatory. For aggression, 6.2% were identified as displaying attention-maintained behavior, 46.9% as tangible-maintained, 59.4% as escape-maintained,
21.9% as discomfort-related and 3.2% as self-stimulatory. For property destruction, 8.7% were
identified as displaying attention-maintained behavior, 26.1% as tangible-maintained, 30.4% as escape-maintained, 4.3% as discomfort-related and 26.1% as self-stimulatory. These differences were significant for self-injury (Q [4] = 16.43, p<0.016) and aggression (Q [4] = 43.59, p<0.016); however there were no significant differences for property destruction (Q [4] =7.89, p>0.016). Pairwise comparisons were conducted to test the hypothesis that the proportion of participants meeting criteria for attention-maintained problem behavior would be less than other functions. For self-injury significant differences were found between the attention andquotesdbs_dbs17.pdfusesText_23
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